🗂️ HashMap & HashSet Implementation (JavaScript)

Implementation of the HashMap and HashSet data structures from scratch in JavaScript, as part of The Odin Project.

This project focuses on understanding how hashing works under the hood — buckets, collisions, resizing, and ensuring efficient data storage and retrieval.

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📚 Overview

🔹 HashMap

A HashMap stores key–value pairs with constant-time average complexity for:

• Insertion (set)
• Lookup (get, has)
• Deletion (remove)

It uses:

• Buckets (arrays) for collision handling
• Resizing (rehashing) when the load factor exceeds 0.75
• Hashing function for string keys

🔹 HashSet

A HashSet stores unique values only (no duplicates).
It is built with the same hashing principles as HashMap, but only tracks keys.

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⚡ Features

HashMap

• set(key, value) → insert or update
• get(key) → retrieve value
• has(key) → check existence
• remove(key) → delete key–value
• length() → number of entries
• clear() → reset map
• keys() → return array of keys
• values() → return array of values
• entries() → return [key, value] pairs
• Auto resizing when load factor exceeded

HashSet

• add(value) → insert unique value
• has(value) → check existence
• remove(value) → delete value
• length() → number of values
• clear() → reset set
• values() → return all values
• Auto resizing when load factor exceeded

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🚀 Getting Started

1. Clone the repository

   git clone https://github.com/devxsameer/odin-hashmap
   cd odin-hashmap

2. Run the example

   node index.js

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🖥️ Example Output

=== HashMap Demo ===
Get name: Sameer
Has city? true
Map length: 3
After removing age, length: 2
Keys: [ 'name', 'city' ]
Values: [ 'Sameer', 'Moradabad' ]
Entries: [ [ 'name', 'Sameer' ], [ 'city', 'Moradabad' ] ]
After clear, length: 0

=== HashSet Demo ===
Has banana? true
Set length: 3
After removing cherry, length: 2
Values in set: [ 'banana', 'apple' ]
After clear, length: 0

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🛠️ Technologies

• JavaScript (ES6+)
• Node.js (for running demo)

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🎯 Learning Outcomes

• Understand hashing functions and collisions
• Implement resizing and rehashing
• See how HashMap and HashSet are built internally
• Practice JavaScript classes and modules

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📝 License

This project is for learning purposes as part of The Odin Project Curriculum. Feel free to fork, play around, and improve!

Built with ❤️ by Sameer Ali.